The vast majority of the world's wastewater does not undergo treatment of any kind before being dumped into the nearest open water source. This has resulted in an international health crisis, where people die daily for lack of clean water. Unstable ecosystems caused by nutrient rich waste runoff are creating high rates of fish kill, ocean floor plant kill and large concentrations of pathogenic bacteria. This is a direct effect of lack of treatment or poor treatment and disposal of such waste streams. Effects such as disastrous algae blooms in open water sources from eutrophic conditions have drastically increased in the past decade and pose unprecedented environmental problems.
Typical prior art wastewater treatment systems typically employ mechanical aeration and chemical treatment. These systems are expensive to build and to operate, not solely because of the high energy costs incurred in the aeration process, but also because of the manpower required to operate the expensive machinery employed in such systems. Such mechanical/chemical treatment facilities, even those that are considered “state of the art,” have a price tag in the millions and even up to hundreds of millions of dollars, making them so expensive that many communities, in the US and other parts of the developed world, have in the past been unable to afford such sewage treatment systems. As a result, the majority of the world's population lives with massive sewage pollution.
Bioremediation of wastewater has been proposed in the past. Such bioremediation systems typically employ a combination of aerobic and anaerobic processes. In particular, such prior art systems have generally proposed the use of anaerobic bacteria for digestion of organic matter and the release of biogas, combined with phototrophic organisms that produce oxygen to accelerate the breakdown of organic matter by aerobic bacteria. (At the same time, the aerobic bacteria produce carbon dioxide which is needed by the phototrophic organisms.) Anaerobic digestion kills most of the pathogenic bacteria found in raw sewage by depriving it of oxygen. In addition, the anaerobic bacteria are able to digest most of the biologically activating solids. Through this anaerobic digestion process, levels of Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) are greatly reduced, in addition to decreasing the amount of solid content in the waste. In this manner, the complementary nature of aerobic and anaerobic processes can be harnessed to break down organic material into its elemental forms without the use of ‘heat, beat and treat’ systems currently used in conventional, mechanical aeration/chemical treatment waste remediation facilities.
Algae has long been proposed as a suitable phototrophic organism for use in such bioremediation of wastes. One large project using such an approach is the St. Helena Wastewater Treatment plant in California, and other such plants have been put into service elsewhere in the world.
These solutions have demonstrated a number of desirable characteristics, but have had significant shortcomings. Because these prior art systems do not have a mechanism for controlling the algal specie(s) present, their algae cultures drift over time, often with unwanted outcomes. These undesirable outcomes include the growth of species that cannot be easily separated from the water at the end of processing; the proliferation of species that grow well during “normal” conditions, but are unable to grow in the case of process excursions, e.g. an influx of an industrial pollutant; or the proliferation of algaie species that grow well, but do not perform all of the desired remediation.
Further, absent a mechanism for active replenishment of the algae, wash-out events (e.g. from a rainstorm) can severely dilute the algae culture density, such that the system is unacceptably slow to return to an effective culture density.
Thus, there has been a long-felt, and growing, need for a wastewater remediation system and method that is cost effective while offering an efficient, stable remediation approach.